Radio transmission control



Dec. 13;, 1949 D. MITCHELL 2,491,276

I RADIO TRANSMISSION CONTROL Filed April 20, 1948 2 sheets-sheet 1 2ALT/METER ALT/METER RECEIVER TRANSMITTER RADIO TRANSMITTER RECEIVERINVEN TOR Q Ml TCHELL qua-O M ATTORNEY Dec. 13, 1949 D, MITCHELL2,491,276

RADIO TRANSMISSION CONTROL Filed April 20, 1948 2 Sheets-Sheet 2 lNl/ENTOR 0. M/TCHELL JQLUWT ATTORNEY Patented Dec. 13, 1949 RADIOTRANSMISSION CONTROL Doren Mitchell, Martinsville, N. 3., asslgnor toBell Telephone Laboratories, Incorporated, New York, N. Y., acorporation of New York Application April 20, 1948, Serial No. 22,229

9 Claims. (Cl. 25017) This invention relates to radio systems and inparticular to systems and methods of controlling the propagation andreception ranges of radio waves.

It is an object of this invention to obtain in an aircraft radio systema constant transmittingrange.

It is another object of this invention to obtain in a radio system aconstant transmitting range irrespective of the height of said system.

It is a further object of this invention to obtain in an aircraft radiosystem, comprising a transmitterconneoted to an antenna, a constanttransmission range without varying the power output'of said transmitter.

It'is' a still further object of this invention to control the range ofa mobile radio transmitter -receiver system in accordance with thealtitude of said system.

It is an additional object of this invention to-control the energyradiated by an antenna in accordance with the height of said antenna.

Dth'er objects and uses of the invention will be apparent from a studyof the specification and drawings.

lit is known that the propagation and reception ranges of radio systemsmay be determined by varying the power output of these systems. Controlsystems have been developed to regulate transmission and receptionranges and while these systems are usually efiicient in operation theyalso have inherent limitations. When, for example, mobile radio systemsare used in airplanes it may be desirable to limit the transmission andreception of the radio system to a twent'y-mile range in order tominimize interference. If a one hundred watt transmitter operating atone hundred and fifty megacyoles is used in an. airplane the transmitterwill have an effective range of about twenty miles when the airplanecontaining the transmitter is situated on the ground. However, as theairplane rises from the ground the transmitter range increases fairlyrapidly to a range of. about two hundred miles, at: an altitude oftwenty thousand feet, and this expandedrange may be an undesirablefeature. In the future, due to the rapid development of the mobile radioart and the resultant extensive use of mobile radio systems byincreasing numbers of people, the extension of the transmission andrecaption ranges of a radio system may result in unwanted crosstalk andother interferences. The invention maintains a substantially constantrange in a radio system by eiiectively limiting the radio systemtransmission-reception distances in accordance with the altitudes of theradio system radiating and receiving members.

In the preferred embodiment of the invention the control of a radiosystem transmission and/ or reception range is varied automatically inaccordance with the height of the system transmittingreceiving membersin relation to the earth. In the invention an automatic coupling systemmay vary the radiated power output of a radio trans-- mitter, or thepower input of a radio receiver, in response to variations in thealtitude of the transmitting or receiving antennae. In an alternativeembodiment of the invention the automatic coupling system responds tovariations in the pressures of the atmosphere.

Referring to the drawings:

Fig. l is a schematic drawing of an embodi ment of the invention andshows equipment for automatically controlling the ranges of atransmitter-receiver radio system in accordance with variations inaltitude;

Fig. 2 is a schematic drawing of an alternative embodiment of the systemshown in Fig. 1, and shows equipment for automatically controlling theranges of a' transmitter-receiver radio system in accordance withvariations pressures; and

Fig. 3 is a schematic drawing and shows the control system of Fig. 1and/or Fig. 2 utilized in an airplane.

Referring to Fig. l which is a schematic drawing of an embodiment of theinvention, a shaft l0, adapted for rotative movement in clockwise orcounter cl'ockwise directions, may be actuated through. connecting gearsH and I2 by a drive shaft it which may be motivated by a reversiblemotor It. The shaft it has an antenna connection 15 from an antenna it,an antenna pick-up loop 11, a ground connection is, and an absorptionloop l8 withwhich is connected. a dissipation resistance 26 Theequipment units 55, ii, l8, l9 and 2d are electrically divided asillustrated by insulated segments 23, 22, 23, and 2 3 of the shaft i6.Positioned for inductive coupling to the pickin atmospheric up loop IT,or to the absorption loop !9, is a loop 25 which is connected to a radiotransmitter-receiver 26. Secured to an end of the shaft til is aposition indicatin pointer 2i. The pointer 21 turns withv the shaft Illand. moves over a chart 28, which may be calibrated in angles ofdegrees.

so that the position of the pointer 2? in relation. to the chart 28' mayinform an observer at any instant of the angular position of the shaftH).

The reversiblev motor is may be energized from an electromotive source29 through operatedcon- 3 tacts of a relay 3!], or may be energized torotate in an opposite direction through the operated contacts of a relay3|. The motor it may be so connected that operation of the relay 38actuates the motor M in a counter-clockwise direction and the motor Macting upon the shaft it, through the gears i l and I2, turns the shaftH3 in a clockwise direction, while operation of the relay 3i may causethe motor M to turn the shaft iii in a counter-clockwise direction. Theoperation circuits of the relays and 3| are controlled fromelectromotive sources 32 and 33 through potentiometers 34 and 35, andthrough potentiometer slider arms 36 and 31. The voltage potentialacross the electromotive source 32 is preferably equal to the voltagepotential across the electromotive source 33, and the resistances of.the potentiometers 34 and should also be of equal value.

The potentiometer slider arm 37 is mechanically connected to the shaft II] and movement of the shaft it! moves the potentiometer slider arm 3!in a corresponding direction. The potentiometer slider arm 36 isconnected to an indication needle 38 of an electronic altimeter system39. Movement of the indicator 38 upon an altimeter indicating dial 40results in a movement of the potentiometer slider arm 36 in acorresponding direction. The electronic altimeter system 39 may be of atype known in the art such as that system disclosed in Patent 2,247,662issued July 1, 1941 to R. C. Newhouse.

The system embodiment in accordance with the invention operates asfollows. Suppose that the system is installed as a part of a mobileradio system in an airplane. When the airplane is situated on the groundthe antenna pick-up loop ll will be positioned for optimum inductivecoupling to the radio transmitter-receiver loop 25. When the pick-uploop I! is so situated, the potential between a point 4H and the tip ofthe potentiometer slider arm 36 will equal the potential between thepoint 4! and the tip of the potentiometer slider arm 31. Since thesepotentials oppose each other there is no potential difference betweenthe tips of the slider arms 36 and 31, and no current will flow fromthese tips through the relay energizing circuits. When the airplanerises into the air and has attained a certain altitude the electronicaltimeter needle 33 will have moved to a new position 38' in relation tothe altimeter indicator dial Ml, and will have moved the potentiometerslider arm 3% to a new position 36'. When the slider arm 36 occupies thenew position 36' the potential between the point 4! and the tip of theslider arm 3% in position 36 will be less than the potential between thepoint 4| and the tip of the slider arm 31, and current will flow to thetip of the slider arm 36 and thence through a circuit, including aunidirectional conducting valve 4 2, to energize and operate the relay3!. Operation of the relay 3| energizes the motor It so that the shaftit turns in a counter-clockwise direction as discussed. Thecounter-clockwise movement of the shaft l0 swings the antenna pick-uploop H away from the transmitter-received loop 25, so as to reduce thecoupling between the loop I! and the loop 25, and at the same timeswings the absorption loop I 9 into a more favorable coupling positionso as to increase the coupling between the loop i9 and thetransmitter-receiver loop 25. This action diverts a portion of theenergy from the radio transmitter-receiver 23 into the absorption loop19 and prevents some of this energy portion from reaching the antennal6, for some of the energy diverted into the absorption loop [9 isdissipated in the resistance 23. The use of the absorption loop providesrange control of the mobile radio system, equalizes the load on thetransmitter and facilitates the tuning of the transmitter.

As the shaft It] turns in a counter-clockwise direction the slider arm3'! turns with the shaft it until it reaches a new position 31. When theslider arm 3! has reached the position 3'! the voltage potential betweenthe point 4! and the tip of slider arm 36 in position 36 will equal thevoltage potential between the point M and the tip of the slider arm 3'!in position 31. Since these potentials opposed each other there is nopotential difference between the tips of the slider arms 36 and 31 inpositions 36' and 31', and no current will flow to the relay energizingcircuit and the relay 3| will restore to a normal nonoperated conditionand stop the movement of the motor M. When the motor i4 stops, theturning movement of the shaft Ill ceases and the shaft it] comes to restwith the loops I1 and I9 retaining their new positions in relationshipto the transmitter-receiver loop 25.

When the airplane loses altitude the altimeter needle 38 will move backfrom the position 38 towards the zero position on the altimeter dial 4%]until it reaches a position at which it will indicate the new altitudeof the airplane in relationship to the earth. The backward movement ofthe needle 38 will move the slider arm 33 back from the position 36'towards the position originally occupied by the slider arm 36 beforealtitude was attained. When the slider arm 36 occupies the new positionthe potential from the point M to the tip of the slider arm 31, inposition 37', will be less than the potential between the point 4| andthe tip of the slider arm 38, and current will flow to energize andoperate the relay 30 through a circuit including the slider arm 3'! inposition 31, the relay 3D, and a unidirectional conducting valve 43.Operation of the relay 3!! actuates the motor it and causes the shaft mto turn in a clockwise direction as discussed. The shaft l [i whenturning in a clockwise direction moves the absorption loop away from thetransmitter-receiver loop 25, and moves the antenna loop I! into abetter coupling position in relationship to the transmitter-receiverloop 25. The turning movement of the shaft Ill also moves the slider arm31 back from the position 31', towards the original position it occupiedbefore the airplane attained altitudes, until the.

slider arm 31 reaches a point on the potentiometer 35 whereat thepotential from the point 4! to the tip of the slider arm 36 is equal tothe potential from the point 4! to the tip of the slider arm 31. Whenthe condition of equal potentials is attained no current flows to therelay energizing circuits, the relay 3!! will then restore to a normalnon-operated position and the turning movement of the shaft ill willcease.

It will be readily understood that while the system as shown utilizesone antenna for both transmission and reception purposes a plurality ofantennae may be utilized. The automatic control features in accordancewith the invention may also be utilized by the transmitter mechanismalone, while the receiver mechanism may operate normally and use aseparate antenna without the automatic control feature.

Referring to Fig. 2, there is shown an alternate embodiment of theinvention for automatically controlling the range of a radio system inaccordance with variations in atmospheric pressures. Here is shown adisk 45 with a pin 46 attached to the disk. The disk 45 is adapted forconnection to the coupling mechanism of Fig. 1 along the section markedXX. The pin 46 is connected by a crank 4'! to a bellows mechanism 48which is preferably sealed at sea level atmospheric pressure. Thisequipment is adaptable for use in an airplane for controlling thecoupling between the pick-up loop H, the absorption loop l9 and thetransmitter-receiver loop 25 of Fig. 1.

This system operates as follows. When the airplane is situated upon theground the bellows 48 being subjected to ground level atmosphericpressure is in a normally contracted condition. When the airplane leavesthe ground and gains altitude the atmospheric pressure decreases and thebellows mechanism expands and occupies a new position 48'. Expansion ofthe bellows actin through the crank 41 upon the pin 46 pushes the pin 46to a new position 46', and turns the shaft in a counter-clockwisedirection moving the pick-up loop I! away from the transmitterreceiverloop 25, in a manner discussed in relation to Fig. 1. As the airplaneloses altitude the bellows is compressed and contracts due to increasedatmospheric pressure, and the pin 46 moves from the position 46' backtowards the original osition it occupied when the airplane was situatedon the ground, and moves the absorption loop 19 away from thetransmitter-receiver loop 25, in a manner discussed in relation to Fig.1.

Referring to Fig. 3 which is a schematic drawing showing the automaticrange control systems of Figs. 1 and 2 utilized in an airplane, Fig. 3shows antennae 5| and 52 of an electronic altimeter system correspondingto the antennas of the altimeter 39 of Fig. 1, and antenna 53 of atransmitter-receiver system corresponding to antenna I6 together with abellows mechanism 54.

It is to be understood that the above-described embodiments areillustrative examples and that various modifications may be made withoutdeparting from the spirit of this invention.

What is claimed is:

1. In a mobile radio system, the combination of a transmitter, aradiating member, a dissipation member, separate adjustable rotatableelements for coupling said members to said transmitter, and meansresponsive to changes in atmospheric pressure for simultaneouslyrotating said elements in a clockwise or counter-clockwise directiondependent upon the sense of the change in said pressure, whereby thecouplings of said members to said transmitter are varied in oppositesenses upon any change in said pressure and the sense of the variationfor each coupling is reversed upon a reversal in the sense of the changein said pressure.

2. The combination of claim 1 in which the responsive means isresponsive to changes in the altitude of said radiating member.

3. In a mobile radio system the combination of, a transmitter-receiver,a radiating member, a dissipation member, movable coupling loops forcoupling said members to said transmitter-receiver, and means responsiveto changes in at-- mospheric pressure due to changes in altitude forvaryin the positions occupied by said loops in their relationships tosaid transmitter-receiver.

4. In a radio system the combination of a transmitter, a radiatingmember, a dissipation member, an adjustable coupling element includedbetween said transmitter and said members and means responsive tochanges in the altitude of said system for controllin the adjustment ofsaid element.

5. In a mobile microwave radio system comprisin a transmitter, aradiating member, a dissipative member, and separate adjustable elementscoupling said members to said transmitter, the method comprisingdecreasing the coupling of said radiating member and simultaneouslyincreasing the coupling of the dissipative member upon an increase inthe altitude of said system, and increasing the coupling of saidradiating member and simultaneously decreasing the coupling of saiddissipative member upon a decrease in said altitude.

6. In a system for rendering the effective range of a radio systemindependent of the height of said system, the method comprising changingthe amounts of energy emitted and received by said system inversely inaccordance with changes in the height of said system.

7. In a system for maintaining constant the range of a mobile radiosystem irrespective of variations in the altitude of said radio systemand without changing the power output of said radio system, the methodcomprising, radiating the entire output of said radio system when saidradio system is situated at a minimum altitude, radiating a portion ofsaid output and dissipating the remaining output portion when said radiosystem is situated at a different altitude, and progressively decreasingthe ratio of said radiated portion to said dissipated portion as thealtitude increases.

8. In a system for maintaining constant the range of a mobile radiosystem irrespective of changes in the altitude of said radio system andin the atmospheric pressures surrounding said system, and withoutchanging the power of said radio system, the method comprisingefliciently utilizing the power of said radio system when said radio issituated at a minimum altitude, efficiently utilizing a portion of saidpower and dissipating the remaining portion when said radio attains adifferent altitude, and progressively decreasing the ratio of saideiliciently utilized power portion to said dissipated power portion asthe altitude increases, while increasing said ratio as the altitudedecreases.

9. The method of radio communication from an airborne vessel whichcomprises continuously measuring the height of the vessel above theearths surface and continuously controlling the intensity of the radiofrequency energy transmitted from the vessel for communication undercontrol of the height indication to cause that energy to vary inverselywith the height.

DOREN MITCHELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,008,832 Leonard, Jr July 23,1935 2,190,037 Neufeld "Feb. 13, 1940 2,378,604 Wallace ..June 19, 19452,403,603 Korn July 9, 1946 FOREIGN PATENTS Number Country Date 372,819Great Britain May 12, 1982

